A systematic study of coupled heat and mass transfer in unsaturated soils under complex boundary conditions was carried out and a mathematical model of heat and mass transfer in unsaturated soils was established by no...A systematic study of coupled heat and mass transfer in unsaturated soils under complex boundary conditions was carried out and a mathematical model of heat and mass transfer in unsaturated soils was established by non equilibrium thermodynamic theory. The gradient of volumetric moisture content, the gradient of temperature, the salt mass concentration and vapor pressure were the primary driving forces influencing the process of heat and mass transfer in unsaturated soils. Based on the thermodynamic analysis and the mass and energy conservation principles, a set of mass and energy equations were developed. The initial and boundary conditions of soil column for one dimension were also given out.展开更多
Different types of vegetation occupy different geomorphology and water gradient environments in the San- jiang Plain, indicating that the soil moisture dynamics and water balance patterns of the different vegetation c...Different types of vegetation occupy different geomorphology and water gradient environments in the San- jiang Plain, indicating that the soil moisture dynamics and water balance patterns of the different vegetation communi- ties might differ from each other. In this paper, a lowland system, perpendicular to the Nongjiang River in the Honghe National Nature Reserve （HNNR）, was selected as the study area. The area was occupied by the non-wetland plant forest and the typical wetland plant meadow. The Microsoft Windows-based finite element analysis software package for simulating water, heat, and solute transport in variably saturated porous media （HYDRUS）, which can quantita- tively simulate water, heat, and/or solute movement in variably-saturated porous media, was used to simulate soil moisture dynamics in the root zone （20-40 cm） of those two plant communities during the growing season in 2005. The simulation results for soil moisture were in a good agreement with measured data, with the coefficient of determi- nation （R2） of 0.44-0.69 and root mean square error （RMSE） ranging between 0.0291 cm3/cm3 and 0.0457 cm3/cm3, and index of agreement （d） being from I）.612 to 0.968. During the study period, the volumetric soil moisture content of meadow increased with the depth and its coefficient of variation decreased with the depth （from 20 cm to 40 cm）, while under the forest the soil moisture content at different depths varied irregularly. The calculated result of water budget showed that the water budget deficit of the meadow was higher than that of the forest, suggesting that the meadow is more likely to suffer from water stress than the forest. The quantitative simulation by HYDRUS in this study did not take surface runoff and plant growth processes into account. Improved root water uptake and surface runoff models will be needed for higher accuracy in further researches.展开更多
Based on the multiphase poroelasticity theory describing the propagation of waves in the unsaturated fluid-saturated porous medium,the reflection and transmission coefficients of the seismic waves at the interface bet...Based on the multiphase poroelasticity theory describing the propagation of waves in the unsaturated fluid-saturated porous medium,the reflection and transmission coefficients of the seismic waves at the interface between soil layers with different saturations are obtained.Our unsaturated model consists of a deformable skeleton in which two compressible and viscous fluids(i.e.,water and gas)flow in the interstices.Three compressional waves(i.e.,P1,P2,and P3 waves)and one shear(i.e.,S wave)wave exist in the unsaturated soils.The expressions for the energy ratios of the various reflected and transmitted waves at the interface during the transmission and reflection processes are presented in explicit forms accordingly.At last,numerical computations are performed and the results obtained are respectively depicted graphically.The variation of the energy ratios with the incident angle,wave frequency and saturation degrees of the upper and lower soil layers is illustrated in detail.The calculation results show that the allocation of incident seismic waves at the interface is influenced not only by the angle and frequency of the incident seismic waves,but also by the saturations of the upper and lower soil layers.It is also verified that,at the interface,the sum of energy ratios of the reflected and transmitted waves is approximately equal to unity as was expected.This study is of importance to several fields such as geotechnical engineering,seismology,and geophysics.展开更多
文摘A systematic study of coupled heat and mass transfer in unsaturated soils under complex boundary conditions was carried out and a mathematical model of heat and mass transfer in unsaturated soils was established by non equilibrium thermodynamic theory. The gradient of volumetric moisture content, the gradient of temperature, the salt mass concentration and vapor pressure were the primary driving forces influencing the process of heat and mass transfer in unsaturated soils. Based on the thermodynamic analysis and the mass and energy conservation principles, a set of mass and energy equations were developed. The initial and boundary conditions of soil column for one dimension were also given out.
基金Under the auspices of National Natural Science Foundation of China (No. 40871241,41001050)Direction Project of Chinese Academy of Science (KZCX2-YW-Q06-03)
文摘Different types of vegetation occupy different geomorphology and water gradient environments in the San- jiang Plain, indicating that the soil moisture dynamics and water balance patterns of the different vegetation communi- ties might differ from each other. In this paper, a lowland system, perpendicular to the Nongjiang River in the Honghe National Nature Reserve （HNNR）, was selected as the study area. The area was occupied by the non-wetland plant forest and the typical wetland plant meadow. The Microsoft Windows-based finite element analysis software package for simulating water, heat, and solute transport in variably saturated porous media （HYDRUS）, which can quantita- tively simulate water, heat, and/or solute movement in variably-saturated porous media, was used to simulate soil moisture dynamics in the root zone （20-40 cm） of those two plant communities during the growing season in 2005. The simulation results for soil moisture were in a good agreement with measured data, with the coefficient of determi- nation （R2） of 0.44-0.69 and root mean square error （RMSE） ranging between 0.0291 cm3/cm3 and 0.0457 cm3/cm3, and index of agreement （d） being from I）.612 to 0.968. During the study period, the volumetric soil moisture content of meadow increased with the depth and its coefficient of variation decreased with the depth （from 20 cm to 40 cm）, while under the forest the soil moisture content at different depths varied irregularly. The calculated result of water budget showed that the water budget deficit of the meadow was higher than that of the forest, suggesting that the meadow is more likely to suffer from water stress than the forest. The quantitative simulation by HYDRUS in this study did not take surface runoff and plant growth processes into account. Improved root water uptake and surface runoff models will be needed for higher accuracy in further researches.
基金supported by the National Natural Science Foundation of China(Grant No.51378258)the National Basic Research Program of China("973"Project)(Grant No.2011CB013601)
文摘Based on the multiphase poroelasticity theory describing the propagation of waves in the unsaturated fluid-saturated porous medium,the reflection and transmission coefficients of the seismic waves at the interface between soil layers with different saturations are obtained.Our unsaturated model consists of a deformable skeleton in which two compressible and viscous fluids(i.e.,water and gas)flow in the interstices.Three compressional waves(i.e.,P1,P2,and P3 waves)and one shear(i.e.,S wave)wave exist in the unsaturated soils.The expressions for the energy ratios of the various reflected and transmitted waves at the interface during the transmission and reflection processes are presented in explicit forms accordingly.At last,numerical computations are performed and the results obtained are respectively depicted graphically.The variation of the energy ratios with the incident angle,wave frequency and saturation degrees of the upper and lower soil layers is illustrated in detail.The calculation results show that the allocation of incident seismic waves at the interface is influenced not only by the angle and frequency of the incident seismic waves,but also by the saturations of the upper and lower soil layers.It is also verified that,at the interface,the sum of energy ratios of the reflected and transmitted waves is approximately equal to unity as was expected.This study is of importance to several fields such as geotechnical engineering,seismology,and geophysics.
